The physical properties of nanoparticles (“NPs”), e.g., high surface-to-volume ratio, elevated surface energy, increased ductility after pressure loading, higher hardness, larger specific heat, and the like, have led to increased applications in the material-directed industry and material science. For example, a variety of metal NPs have been used to catalyze numerous reactions.
The size of NPs range from less than 1 nm to about 100 nm and the electronic energy band configuration is a size-dependent property, which in turn can affect the physical and chemical properties. A fundamental distinction between NPs and bulk materials is that the fraction of surface atoms and the radius of curvature of the surface of NPs is comparable with the lattice constant. As a result, nanostructured catalysts generally have a higher catalytic activity as compared with their analogues based on bulk materials. A number of methods of forming NPs are known to the skilled artisan and include formation by combining atoms (or more complex radicals and molecules) and by dispersion of bulk materials, e.g., thermal evaporation, ion sputtering, reduction from solution, reduction in microemulsions, and condensation.
Colloidal particles used in sensing arrays have been reported. These are chemical sensors for detecting analytes in fluids via arrays having a plurality of alternating nonconductive regions and conductive regions of conductive NP materials. Variability in chemical sensitivity from sensor to sensor is reported to be provided by qualitatively or quantitatively varying the composition of the conductive and/or nonconductive regions.
Single particle electrochemical sensors, which employ an electrochemical device for detecting single particles, have also been reported. Methods for using such a device to achieve high sensitivity for detecting particles such as bacteria, viruses, aggregates, immuno-complexes, molecules, or ionic species have also been described.